tcp: TCP Fast Open Server - support TFO listeners

[mirror_ubuntu-zesty-kernel.git] / net / ipv4 / tcp_timer.c

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index b774a03bd1dcc1ccafa245a892ac0b312511a900..fc04711e80c89dd0dc92ff1027efaa7324b218c3 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -304,6 +304,35 @@ static void tcp_probe_timer(struct sock *sk)
        }
 }
 
+/*
+ *     Timer for Fast Open socket to retransmit SYNACK. Note that the
+ *     sk here is the child socket, not the parent (listener) socket.
+ */
+static void tcp_fastopen_synack_timer(struct sock *sk)
+{
+       struct inet_connection_sock *icsk = inet_csk(sk);
+       int max_retries = icsk->icsk_syn_retries ? :
+           sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
+       struct request_sock *req;
+
+       req = tcp_sk(sk)->fastopen_rsk;
+       req->rsk_ops->syn_ack_timeout(sk, req);
+
+       if (req->retrans >= max_retries) {
+               tcp_write_err(sk);
+               return;
+       }
+       /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
+        * returned from rtx_syn_ack() to make it more persistent like
+        * regular retransmit because if the child socket has been accepted
+        * it's not good to give up too easily.
+        */
+       req->rsk_ops->rtx_syn_ack(sk, req, NULL);
+       req->retrans++;
+       inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+                         TCP_TIMEOUT_INIT << req->retrans, TCP_RTO_MAX);
+}
+
 /*
  *     The TCP retransmit timer.
  */
@@ -317,7 +346,15 @@ void tcp_retransmit_timer(struct sock *sk)
                tcp_resume_early_retransmit(sk);
                return;
        }
-
+       if (tp->fastopen_rsk) {
+               BUG_ON(sk->sk_state != TCP_SYN_RECV &&
+                   sk->sk_state != TCP_FIN_WAIT1);
+               tcp_fastopen_synack_timer(sk);
+               /* Before we receive ACK to our SYN-ACK don't retransmit
+                * anything else (e.g., data or FIN segments).
+                */
+               return;
+       }
        if (!tp->packets_out)
                goto out;